Between March, 1974 and March, 1975 we propose to study the regional intrapulmonary distribution on inspired gas and perfusion in anesthetized, paralyzed and mechanically ventilated subjects who are in various body positions (supine, prone and lateral decubitus). We also plan to examine the effect of various inhalation anesthetics on intrapulmonary gas and blood flow distribution. In addition, we plan to measure the closing volumes and inspiratory and expiratory flow rates of individual lungs during the single breath oxygen test in sedated volunteers. These studies will be performed while the subjects are in the aforementioned body positions.